-LRB- CNN -RRB- -- If the moon looks a little bit bigger and brighter this weekend , there 's a reason for that . It is .

Saturday 's full moon will be a super `` perigee moon '' -- the biggest in almost 20 years . This celestial event is far rarer than the famed blue moon , which happens once about every two-and-a-half years .

`` The last full moon so big and close to Earth occurred in March of 1993 , '' said Geoff Chester with the U.S. Naval Observatory in Washington . `` I 'd say it 's worth a look . ''

Full moons look different because of the elliptical shape of the moon 's orbit . When it 's at perigee , the moon is about 31,000 miles -LRB- 50,000 km -RRB- closer to Earth than when it 's at the farthest point of its orbit , also known as apogee .

`` Nearby perigee moons are about 14 % bigger and 30 % brighter than lesser moons that occur on the apogee side of the moon 's orbit , '' the NASA website says .

This full moon will rise in the east at sunset and should look especially big at that time because of what 's known as the `` moon illusion . ''

`` For reasons not fully understood by astronomers or psychologists , low-hanging moons look unnaturally large when they beam through trees , buildings and other foreground objects , '' according to NASA .

iReport : Share your photos

Even though it may look close enough to touch , Saturday 's full moon will still be at a healthy distance -- some 211,600 miles -LRB- 356,577 km -RRB- away .

As rare as it is , it may be worth a look . Miss it and you 'll have to wait until 2029 to see it again .

@highlight

The last full moon so big and close to Earth occurred in March of 1993

@highlight

Saturday 's full moon will be the biggest in almost 20 years

@highlight

Saturday 's full moon will still be 211,600 miles away

@highlight

This full moon will appear about 14 % bigger and 30 % brighter